Join on different columns

Question

I want to join 2 dataframes and I'm using the intructions in the Julia guide: http://dataframesjl.readthedocs.org/en/latest/joins_and_indexing.html?highlight=join

join(a, b, on = :ID, kind = :inner)

Now, how I can join on columns with different names:

• :ID for a
• :name_id for b

I tried the following but it doesn't work"

join(a, b, on = [ :ID, :name_id ], kind = :inner)

If not implemented, that would be nice feature

Answer 1

rename!(b, "name_id", "ID")
j = join(a, b, on = :ID, kind = :inner)
rename!(b, "ID", name_id")

The rename changes b, so here I changed it back. (In the general case if there are renaming conflicts within a dataframe you can pick a unique name for each pair of joined names, rename in each dataframe, join and rename back.)

This method is obviously not elegant. It's what I've found so far.

Answer 2

The docs on DataFrames.jl provide this example:

innerjoin(a, b, on = [:City => :Location, :Job => :Work])

So for your example:

j = innerjoin(a, b, on = :ID => :name_id)